Multi-frequency harmonic arrays: initial experience with a novel transducer concept for nonlinear contrast imaging

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Biomedical Engineering

Background:

• Nonlinear contrast imaging modes like second harmonic imaging (HI) and subharmonic imaging (SHI) are vital for clinical use.
• Current transducers for HI and SHI are limited by narrow bandwidth, hindering performance.
• A novel multi-frequency harmonic transducer array (MFHA) concept has been developed to address these limitations.

Purpose of the Study:

• To design and conduct a preliminary evaluation of a novel multi-frequency harmonic transducer array (MFHA).
• To assess the potential of MFHA for broadband contrast-enhanced HI and SHI with high dynamic range.
• To investigate the frequency bandwidth and signal-to-noise ratio (SNR) of the MFHA concept.

Main Methods:

• Designed MFHA consisting of three multi-element piezo-composite sub-arrays (A-C) with specific center frequency relationships (4f(A) = 2f(B) = f(C)).
• Enabled SHI by transmitting on sub-array C and receiving on B (or B to A), and HI by transmitting on A and receiving on B (or B to C).
• Measured transmit and receive pressure levels, and evaluated in vitro HI and SHI signal-to-noise ratios (SNRs) up to 40 dB post-contrast administration.

Main Results:

• Two MFHA prototypes demonstrated a broad frequency bandwidth of at least two octaves.
• In vitro tests achieved SNRs for HI and SHI comparable to regular B-mode imaging.
• The MFHA system outperformed commercially available HI systems in terms of SNR.

Conclusions:

• Initial design and in vitro characterization of two MFHA's were successfully performed.
• MFHAs offer a broad frequency bandwidth, enabling enhanced nonlinear contrast imaging.
• Further research on multi-element MFHAs is necessary to assess their in vivo potential for nonlinear contrast imaging.